The New Zealand Rugby Union (NZRU) has made a formal offer to entice former rugby league star Sonny Bill Williams back home. The centre is currently plying his trade with Toulon in France, having controversially left the 13-man code in 2008.

Reports suggest that All Blacks coach Graham Henry will meet Williams' agent, Khoder Nasser, next week and that the former league international could feature at provincial level in New Zealand this season.

"We've made an offer to Sonny Bill to come and play rugby from July," NZRU acting chief executive Neil Sorensen said. "We think he's a special athlete. For a guy who's still relatively new to the game his potential is enormous. We're really keen for him to be part of our environment."

North Harbour, Auckland and Counties-Manukau are in the frame for Williams' signature but Sorenson insisted that the money on offer was not outrageous. The NZRU will have to fight off competition from Toulon, who have reportedly tabled a four-year deal, and also potentially NRL clubs to land their man.

"He's not being offered ridiculous money," he said. "He is an Auckland boy and so we would imagine his first preference would be in the upper North Island to start with."

Sorensen said that if Williams "had a dream run and all the stars aligned" he could be an option for the All Blacks' end-of-year tour to Hong Kong and Europe. Nasser confirmed that there had been an approach to Williams and also that the NZRU had been professional in their conduct.

"I'll confirm we have talked and there is extreme interest in him," he told The Sydney Morning Herald. "I want to emphasise that I have the utmost respect for the way the All Blacks are handling things."

Williams will start at inside-centre for Toulon as they take on Cardiff Blues in the final of the European Challenge Cup in Marseille on Sunday and there is also speculation that he will return to the boxing ring on Anthony Mundine's undercard in Brisbane on June 30.